Speech retrieval method, speech retrieval apparatus, and program for speech retrieval apparatus

1. A speech retrieval apparatus, comprising:

a keyword acquisition unit configured to acquire a keyword designated by a character string, and a phoneme string or a syllable string, the keyword being stored in a non-transitory computer readable storage medium;

a segment detection unit configured to detect one or more coinciding segments by comparing a character string that is a recognition result of word speech recognition with words as recognition units performed for speech data to be retrieved and the character string of the keyword;

an evaluation value calculation unit configured to calculate an evaluation value of each of the one or more coinciding segments by using the phoneme string or the syllable string of the keyword to evaluate a phoneme string or a syllable string that is recognized in each of the detected one or more coinciding segments and that is a recognition result of phoneme speech recognition with phonemes or syllables as recognition units performed for the speech data, wherein the phoneme string or the syllable string associated with each of the segments is a phoneme string or a syllable string associated with a segment in which a start and an end of the segment is expanded by a predetermined time; and

a segment output unit configured to output a segment in which the calculated evaluation value exceeds a predetermined threshold.

2. The apparatus according to claim 1 , wherein the evaluation value calculation unit is further configured to compare a phoneme string or a syllable string that is an N-best recognition result of phoneme speech recognition with phonemes or syllables as recognition units performed for speech data associated with each of the detected one or more coinciding segments and the phoneme string of the keyword to set a rank of the coinciding N-best recognition result as the evaluation value.

3. The apparatus according to claim 1 , wherein the evaluation value calculation unit is further configured to set, as the evaluation value, an edit distance between a phoneme string or a syllable string that is a 1-best recognition result of phoneme speech recognition with phonemes or syllables as recognition units performed for speech data associated with each of the detected one or more coinciding segments and the phoneme string or the syllable string of the keyword.

4. The apparatus according to claim 3 , wherein the edit distance is a distance matched by matching based on dynamic programming.

5. The apparatus according to claim 1 , further comprising a word speech recognition unit configured to perform word speech recognition of the speech data to be retrieved, with words as recognition units.

6. The apparatus according to claim 1 , further comprising a phoneme speech recognition unit configured to perform phoneme speech recognition of the speech data associated with each of the detected one or more coinciding segments, with phonemes or syllables as recognition units.

7. The apparatus according to claim 1 , further comprising a phoneme speech recognition unit configured to perform phoneme speech recognition of the speech data to be retrieved, with phonemes or syllables as recognition units.

8. The apparatus according to claim 1 , wherein the evaluation value calculation unit is further configured to calculate the evaluation value of each of the one or more coinciding segments using the character string of the keyword to evaluate the character string in each of the detected one or more coinciding segments.

9. The apparatus according to claim 1 , wherein the segment output unit is further configured to adjust the predetermined threshold to alter at least one of a precision value and a recall value of the output segment, the precision value being positively correlated with the predetermined threshold and the recall value being negatively correlated with the predetermined threshold.

10. The apparatus according to claim 9 , wherein the precision value is a ratio of retrieval results satisfying a retrieval request to all documents satisfying the retrieval request.

11. The apparatus according to claim 9 , wherein the recall value is a ratio of retrieval results satisfying a retrieval request to all retrieval results.

12. A non-transitory computer readable storage medium comprising a computer readable program for a speech retrieval apparatus, wherein the program causes the speech retrieval apparatus to:

acquire a keyword designated by a character string, and a phoneme string or a syllable string;

detect one or more coinciding segments by comparing a character string that is a recognition result of word speech recognition with words as recognition units performed for speech data to be retrieved and the character string of the keyword;

calculate an evaluation value of each of the one or more coinciding segments by using the phoneme string or the syllable string of the keyword to evaluate a phoneme string or a syllable string that is recognized in each of the detected one or more coinciding segments and that is a recognition result of phoneme speech recognition with phonemes or syllables as recognition units performed for the speech data, wherein the phoneme string or the syllable string associated with each of the segments is a phoneme string or a syllable string associated with a segment in which a start and an end of the segment is expanded by a predetermined time; and

output a segment in which the calculated evaluation value exceeds a predetermined threshold.

13. The non-transitory computer readable storage medium of claim 12 , wherein the program further causes the speech retrieval apparatus to calculate the evaluation value of each of the one or more coinciding segments using the character string of the keyword to evaluate the character string in each of the detected one or more coinciding segments.

14. The non-transitory computer readable storage medium of claim 12 , wherein the program further causes the speech retrieval apparatus to adjust the predetermined threshold to alter at least one of a precision value and a recall value of the output segment, the precision value being positively correlated with the predetermined threshold and the recall value being negatively correlated with the predetermined threshold.

15. The non-transitory computer readable storage medium of claim 14 , wherein the precision value is a ratio of retrieval results satisfying a retrieval request to all documents satisfying the retrieval request.

16. The non-transitory computer readable storage medium of claim 14 , wherein the recall value is a ratio of retrieval results satisfying a retrieval request to all retrieval results.